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I'm making a mold of a helmet but don't want to lose the original "master". I had originally decided to use plaster but am now going to use RTV silicone as it is more flexible and more friendly with undercuts.

I see that T-Bone used Silicone to make his mold for his son's bucket, but need to know if making a two part mold would be better than a simple one part.

My other query is that if I do go ahead with a two part mold what is the best release agent for RTV silicone to prevent the two halves permanently sticking during the curing process?

Ive used many Latex molds ( w/ a plasterbacking to keep the shape) I usually line the inside of the latex w/ a oil based soap. I cant think of the name of it off the top of my head but i usually paint 2 layers on the latex and blow dry it w/ a hair dryer to speed up the process. Works well and have never had any problems w/ anything sticking to it.

Depending on the shape of the helmet, you can make a one-piece RTV Silicone mold that peels off of like a surgical glove (aka a glove mold) It will need a mother mold of plaster or, better, fiberglass to make the castings the right shape. The good part about a glove mold is that you only need enough silicone to build a mold thick enough to avoid tearing.

RTV Silicone being what it is, it won't stick to anything but itself. If you're determined to make a two-piece mold you can get a silicone release agent from the same place you get the silicone from. The good part about making a two-part mold is that the silicone ends up being able to hold its shape in a fairly simple mold box. Unfortunately, this means a lot more material is needed.

I'm definately set on the 2 part mold. Because of the shape and details in the helmet theres no way that I'm going to be able to peel the mold off once its cured. I've been reading the Thurston James book and checking out some of the pic in MLC's album to get some ideas.

I'm thinking of creating a divide around the middle of the helmet, like the MLC Royal Guard project.

I'm definately set on the 2 part mold. Because of the shape and details in the helmet theres no way that I'm going to be able to peel the mold off once its cured. I've been reading the Thurston James book and checking out some of the pic in MLC's album to get some ideas.

I'm thinking of creating a divide around the middle of the helmet, like the MLC Royal Guard project.

Yep thats exactly what i did on my WW2 helmet that o sculpted. Split the 2 in half w/ cut up soda cans and then painted latex on either side.